Method of assembling phonograph translating devices



Sept? 1, 1953 GUNTER, JR 2,650,953

METHOD OF' ASSEMBLING PHONOGRAPH TRANSLATING DEVICES Filed May 3, 1951J9 4; 25 44 46. .45 0% ENTOR.

1W-xl? ee/ N @QZKM da Patented Sept. 1, 1 953 METHOD OF ASSEMBLIN GPHONOGRAPH TRANSLATING DEVICES Lee Gunter, Jr., Mount Prospect, Ill.,assignor to Shure Brothers, Incorporated, Chicago, Ill., a corporationof Illinois Application May 3, 1951, Serial No. 224,410 6 Claims. (Cl.179-100.41)

This invention relates to a method of assembling phonograph pickupcartridges, more particularly to such a method wherein it is desired toassemble a casing formed in halves, a transducing element, and aphonograph needle chuck into a unitary structure, and itis an object ofthe invention to provide an improved method of this character.

The phonograph pickup of the subject application is disclosed andclaimed in an application of Benjamin B. Bauer, Serial No. 224,339,entitled Phonograph Translating Device, led May 3, 1951, and assigned tothe sam-e assignee as the instant invention.

Phonograph pickups of the character indicated comprise a number ofrelatively small parts, each of which is manufactured to certainspecific dimensions, but with a range of permissible tolerance, as iswell known. In the assembling process, during which the parts to beassembled are chosen at random, it frequently occurs that the partsselected have dimensions which do not lit together in the best possiblemanner even though each of these parts has dimensions within the rangeof tolerance. This occurs because the parts selected have theirtolerances all adding in the same sense, for example all positive and byperhaps the maximum amount. In phonograph pickups of the characterindicated, it is not only necessary for the parts to t together as thetolerances will permit to form the nal product, but certain parts mustalso haveprescribed clearances in order that the necessary vibrationalmovements can occur. It has been found in some instances that partsselected at random and assembled together will produce a pickupin whichthe necessary clearances are lacking thereby resulting in rejection.Accordingly, it is a further object of the invention to provide animproved method for assembling the parts or a phonograph pickup withparts selected at random and without regard to the sense of thedimensional tolerances wherein the relatively movable parts of the finalproduct have the prescribed clearances.

In carrying out the invention in one form, there is provided in aphonograph translating device including a pair of casing halves heldtogether to form a casing: a pair of resilient members inside of thecasing halves and each having an opening therein; a pickup unitincluding a transducing element held at one end in the opening in theresilient members and a phonograph needle chuck cemented to thetransducing element at its other end and in line therewith; and .stopmeans On the casing halves ,for limiting lateral movements of the needlechuck and transducing element; the method of assembling the devicecomprising the steps of assembling one end of the transducing elementinto the opening in the resilient members and the resilient members intothe casing halves to form a nal subassembly, disposing the needle chuckat one end in functional relationship to be with the other end of thetransducing element and while so disposed holding the needle chucksubstantially midway between the stop means and in stressfreerelationship with the transducing element, and oementing the needlechuck and the transducing element together while the needle chuck is sodisposed.

For a more complete understanding of the invention, reference should beha-d to the accompanying drawings in which:

Figure 1 is a perspective view of a phonograph pickup cartridgeassembled according to the in- Vention;

Fig. 2 is an elevational view of the cartridge shown in Fig. 1 with onecasing half removed;

Fig. 3 is a sectional view taken substantially along lines 3-3 of Fig.2;

Fig. 4 is a perspective view of a subassembly in the method according tothe invention;

Fig. 5 is a sectional view taken substantially in the direction ofarrows 5-5 of Fig. 4

Fig. 6 is a view taken in substantially the same direction as that ofFig. 5 after a further step in the method according to the invention,and

Figs. '7, 8 and 9 are fragmentary views illustrating various conditionswhich may arise and their solutions according to the invention.

Referring to the drawings, a pickup 20 assembled according to theinvention is shown comprising a cartridge including a pair of casinghalves 2| and 22 within which is mounted a pickup element 23 including atransducing element 24, for example, a piezoelectric element, a chuck ortransmitting unit 25, and a phonograph needle or stylus 26.

The pickup element is supported within the casing at one end of thepiezoelectric elementl 24 by means of rubber or similar material blocks21 and 23, and the phonograph needle 26 extends outwardly of the casingat the forward end, the piezoelectric element 24, thechuck 25, and theneedle 25 comprising a single element or unit mounted in cantileverfashion. Held within the rear of the cartridge are a pair of terminals29 and 3l which are adapted to be received in suitable sockets onelectrical leads in the phonograph pickup arm, and the other ends of theterminals are adapted to be electrically connected to appropriate sidesof the piezoelectric element by suitable conductors or straps 32 and 33.The weight of the tone arm and pickup cartridge which is permitted torest upon the needle 26 when it engages the groove of a phonographrecord is supported virtually entirely upon the piezoelectric ortransducing element 24 during normal operation. A block of dampingmaterial 3D is disposed between the chuck 25 and an abutment on thecasing but it is of such size and stiffness that it provides very littleif any support for the pickup arm during normal operation. The presenceof the block of damping material assists in preventing excessivedeflections of the chuck when undue forces are exerted on the pickuparm. Since the piezoelectric element 24 may be quite fragile, it isdesirable that the force on the needle26 due to the weight of the tonearm be reduced to as small a value as possible as is consistent withmaintaining suncient force at the stylus to assure that the stylus willproperly follow the record grooves. The stylus moves laterally to andfro in the record groove thereby deilecting the piezoelectric element 24and causing an electrical output to be obtained at terminals 29 and 3l.

The casing halves 2l and 22 may be formed of any material having gooddimensional stability, such for example as Bakelite and plasticmaterials or metal, and are held together with the various partsassembled therein by means of rivets or the like 34 and 35. On theoutside of each of the casing halves there may be a series ofprojections 36 and 31, respectively, which are utilized for holding thecartridge to the phonograph tone arm.

Each of the casing halves 2l and 22 is hollowed out to form a space forthe active elements of the pickup. A series of serrations or grooves 33and 39 are provided on the inside of the casing halves for gripping therubber blocks 21 and 28. The piezoelectric element 24 must be iirmlyheld between the blocks 21 and 28, but it is undesirable to compress theblocks 21 and 28 beyond a certain amount because the piezoelectricelement may be held too tightly. This situation may exist when thedimensions of the various parts are such as to produce a very tight twhich condition may arise when the manufacturing tolerances of the partschosen at random are all in the same sense. Thus, for example, therubber blocks 21 and 28 may, for a particular pickup, be thicker by themaximum amount of the permissible tolerance, and the walls of the casinghalves for this particular pickup may also be thicker by the amount ofthe permissible tolerance. Under these conditions, if the walls of thecasing halves are smooth, that is, the serrations 38 and 39 areeliminated, the rubber blocks 2T and 28 are placed under a much greatercompression than they are when the manufacturing tolerances tend in theother or minimum direction, and consequently the piezoelectric elementmay be hel-d too tightly. it has been found that by utilizing theserrations 38 and 36, the material of the blocks 21 and 26 flows to acertain extent into the serrations, thereby causing much less change inclamping force on the piezoelectric element due to changes in theclamping dimensions.

Each of the rubber blocks 21 and 28 includes an open rectangular groovetherein, which grooves lie opposite each other when the rubber blocksare placed together and thereby form a closed rectangular groove withinwhich the rearward end of the piezoelectric element 24 is received. The

piezoelectric element extends downwardly at an angle so that with thechuck 25 and the needle 26 substantially in line therewith, the end ofthe needle projects outwardly of the pickup and below thereof at thedesired point.

The piezoelectric element 24 may be formed of any material havingpiezoelectric properties and the necessary strength, such as quartz,Rochelle salts or certain ceramic materials, for example. Any shape ofpiezoelectric element ma be used, the elongated and rectangularcrosssectional element shown having been found satisfactory. Other formsof transducers may also be used such, for example, as capacitive,resistive, or magnetic elements which change their propu orties withdeformation.

The chuck 25 includes a pair of prongs 4l and 42 which are arranged tolie on the two sides, respectively, of the forward end of thepiezoelectric element, the chuck and the piezoelectric element beingfirmly held together by means of cement i9 or the like. A layer ofinsulating and/or vibrational isolating material, such as a thin sheetof rubber 43, may be cemented iirmly to the forward end of thepiezoelectric element and thus lie between the piezoelectric element andthe prongs 4l and 42.

The chuck 25, as is described more completely in the Bauer applicationreferred to hereinbefore, may be formed by taking a tube of the desiredmaterial, for example steel or aluminum, of the desired length andflattening one end of it until the two portions of the tube lie againsteach other, and flattening the other end so as to be within the sameplane generally as the first part by leaving a space or slot withinwhich the end of the needle 26 may be received. A hole 44 is providedthrough the forward part of the chuck for receiving a detent provided onthe needle 26. The prongs 4| and 42 preferably are larger at their basesthan at their ends to increase their strength and result in a generallytrapezoidal groove within which the end of the piezoelectric element isreceived.

When chuck 25 is cemented to piezoelectric element 24 as described, arelatively rigid structure is formed so that when the needle 26 isengaged within the chuck and the end of the needle is moved back andforth laterally by the record groove, the piezoelectricl element 24 isplaced under bending stresses. The casing halves are provided with stops45 and 46, respectively, against which the edges of the chuck 25 bear soas to limit deflections of the piezoelectric element. lThis is desirablesince the piezoelectric element is fragile and cannot be stressed beyonda certain limit without being subject to breakage. The stops 45 and 46extend inwardly a sufcient distance so that contact therewith is madebefore the piezoelectric element is subjected to the suiicient stress tocause breakage, allowing, however, sucient clearance between stops andthe edges of the chuck necessary for proper operation.

It is essential that the chuck 25 be accurately disposed substantiallyequidistant from the stops 45 and 46 and remain so after the apparatusis assembled in order that the chuck can move laterally in eachdirection by the same amount. In this fashion sound is most faithfullyreproduced. It has been found that during the manuacturing process thedimensions of the parts due to the permissible tolerances are such thatthe piezoelectric element may lie at a slight angle relative to thecasing instead of being centrally disposed therein or the piezoelectricelement may lie slightly offset from the axis of the pickup but parallelthereto.

Ihree possible conditions which may arise are illustrated in Figs. '7, Sand 9. In these figures the dot-dash line il represents the center lineof the pickup as lwell as the aXis of the pickup unit comprising thepiezoelectric element 24, the chuck 25, and the needle 26. The casinghalves 2| and 22 are represented by the stops 45 and 4 6. The directionof View of Figs. 7, 8 and 9 may be the same as that in Figs, 3, 5 and 6,which may be the direction a workman would look when assembling thedevice. In Fig. 7 the piezoelectric ele ment 24 is laterally offset fromthe center line but parallel to it. In Fig. 8 the piezoelectric element2li has its forward end lying on and being bisected by the center line4T, but has its rearward end laterally displaced from the center` line.In Fig. 9 the piezoelectric element 24 has its rearward end on andbisected by the center line 47 and has its forward end laterallydisplaced therefrom. The chuck 25 is shown in each of the Figs. 7, 8 and9 in a dotted position also, which is the position the chuck wouldoccupy if the center line thereof `were coincident with the center lineof the piezoelectric element 2d in each of the positions shown. It willbe observed in Fig. '7 that the chuck 25 (dotted position) is virtuallytouching the stop 45 while it is spaced farther away from stop 46 thanis normal, and in Figs. 8 and 9 that the chuck 25 (dotted position) isvirtually touching the stop 46 while it is spaced farther away from stop45 than is normal, as may be seen in Figs. 3 and 6 wherein the chuck liboccupies the proper position between the stops l5 and iiii. In each ofthe instances of Figs, '7, 8 and 9 wherein the chuck 25 is shown dotted,it will be clear that the chuck may vibrate farther in one directionthan in the other and may hit one of the stops during normal operationwith consequent poor sound reproduction.

These and other instances may be obviated according to the method of theinvention by first assembling the transducing or piezoelectric element24, the rubber blocks 2l' and 28, and the casing halves 2l and 22together as a single unit, followed by assembling the Vchuck to thepiezoelectric elernent and cementing the two, as will now be described.

According to the steps of the invention, the rubber blocks 2l and 23,the piezoelectric element 2d, and the casing halves may be assembled toegether as a unit or a subassembly with the rivets ifi and 35 holding theunit together in any desired way. For example, the rubber block 23 maybe disposed within the hollow of casing half 2i with the back of therubber block in contact with the serrations 39. In this position arectangular groove in the lower portion of rubber block 28 is exposedand the piezoelectric element 24 may be disposed therein substantiallyas shown in solid lines in Fig. 4. The rubber block 2l may then besimilarly assembled against the serrations 38 of casing half 22 and thetwo casing halves placed in proper position opposite each other and thevrivets 34 and 35 applied, the resulting construction being that of Fig.4 as shown by the solid and the phantom lines together and that of Fig.5. The insulating and/or vibrational damping material 41% may be appliedto the end of the piezoelectric element before it is assembled into thecasing halves or afterwards, as may be desired.

After this subassembly has been made, the

piezoelectric element 24 may occupy the correct or center line position,as may be seen in Fig. 5, or any one of the positions shown in Figs. 7,8 and 9, or perhaps others, these positions arising, as has already beenindicated, by slight differences in dimensions of the parts, whichdifferences however are within the manufacturing tolerances. Thedisplacement of the piezoelectric element 24, as shown in Figs. 7, 8 and9, is ex aggerated in order to bring out the conditions had in mind withclarity.

After the subassernbly of Figs. 4 and 5 has been made, the chuck 25 isdisposed between the stops 45 and 46 substantially equidistantly bymeans of shims 4% or other spacers. The prongs di and 42 are disposed soas to lie one on each side of the right end of piezoelectric element 2s.In order to assist the handling of the chuck 25 in this position, itbeing borne in mind that the chuck 25 as well as the other parts aresmall parts and are handled by small implements such as forceps, a smalldab of fluid cement may be placed at the end of the piezoelectricelement 2d and the prongs 4i and 42. The cement becomes tacky and holdsthe chuck and the piezoelectric element slightly while the shims may bedisposed to accurately place the chuck between the stops 45 and 46. Thechuck is, so to speak, held in a functional relationship to be withrespect to the piezoelectric element. In placing the chuck with theprongs di and l2 into cooperative relationship with the end ofpiezoelectric element 2d, there is no stress placed upon thepiezoelectric element and consequently it is not deflected from theposition which it has by virtue of its assembly in the casing halves, asalready described. After the correct placement has been reached, aproper amount of cement 49 is placed over the prongs 4i and 42 and thecoacting end of the piezoelectric element.

In the structure of Fig. 6, it is only necessary for the chuck 25 to beequidistantly disposed between stops 45 and i6 and the chuck pushedrearwardly until the end of the piezoelectric element is received withinthe base of the trapezoidal groove. Thereafter the cement i9 may beapplied and allowed to harden after which the shirns 48 are removed andthe pickup is ready to have the needle inserted into the chuck.

In Fig. 7, and considering the instance where the chuck is shown dotted,it will be understood that if shiins or other spacers were utilized toforce the chuck to occupy a central position between stops i5 and @t andone in which the center line of the chuck 1lies on the center line fi'i,the piezoelectric element 2d would be bent and consequently would havestress therein. Then, when the shims were removed after cement isapplied to the conforming parts and allowed to harden, it is clear thatthe chuck would not occupy a central position between stops i5 and dii.The shims 48 are so placed that the chuck 25 is substantiallyequidistant between the stops dii and 46 and the prongs 4l and l2 areallowed to take their places on the respective sides of thepiezoelectric element `as they will, the base of the trapezoidal groove,however, being disposed against the adjacent end of the piezoelectricelement. In this position of the piezoelectric element and the chunk,there is no stress between these two parts. Consequently, cement may be:applied, allowed to harden, and the shims it removed, and the chuck 25remains relative to the piezoelectric element in the position shown bysolid lines.

In Fig. 8 the same procedure is followed, that is, the chuck 25 isplaced with the prongs il and 152 on opposite sides, respectively, ofpiezoelectric element 24, and shims 8 are so arranged as to space thechuck 25 equidistantly between. the stops L15 and t5. It will beobserved in this gure that with the forward end of the piezoelectricelement lying on the center line 4l, the chuck 25 lies on the centerline 47 also. There is no stress between the chuck and the piezoelectricelement in the position shown by the solid lines, and after cement isapplied to the prongsY and the cooperating end of the piezoelectricelement, allowed to harden and the shims removed, the parts will remainas shown by the.l solid lines.

In Fig. 9 the same procedure also is followed, that is, the chuck 25 isplaced with the prongs ii and i2 on opposite sides, respectively, of theforward end oi piezoelectric element and shims. d8 are disposed so as toplace the chuck midway between the stops d and 6, there being no stressbetween the chuck and the piezoelectric element. Cement applied to theprongs 4i and 42 and the cooperating end of the piezoelectric elementand allowed to harden will hold the parts in the relative positionshown. Thereafter the shinis may be removed.

When assembled as described, the chuck 25 will lie substantially midwaybetween stops i5 and it and consequently vibrations may occur equally inboth directions with resulting good reproduction of sound.

While particular embodiments of the invention have been shown, it willbe understood, of course.. that the invention is not limited theretosince many modiiications may be made, and it is, therefore, contemplatedby the appended claims to cover any such modications as fall withinthe.- true spirit and scope of the invention.

The invention having thus been described, what is claimed and desired tobe secured by Letters Patent is:

l. In a phonograph translating device including a pair of casing halvesheld together to form a casing; a pair of resilient members inside ofsaid casing halves and having an opening therein; a pickup unitincluding, la transducing element held at one end in said opening and aphonograph needle chuck cemented to such transducing element in linetherewith at its other end; and stop means on said casing halves forlimiting lateral movements of such needle chuck and transducing element;the method of assembling said device comprising the steps of assemblingone end of said transducing element into the opening in said resilientmembers and said resilient members into said casing halves to form ainal subassembly, disposing said needle chuck with one end in functionalrelationship to be with the other end of said transducing element andwhile so disposed holding said needle chuck substantially midway betweensaid stops and in stress-free relationship with said transducingelement, and cementing said needle chuck and said transducing elementtogether While said needle chuck is so disposed.

2. In a phonograph translating device including a pair of casing halvesheld together to form a casing; a pair of resilient members inside ofsaid casing halves and having an opening therein; a pickup unitincluding, a piezoelectric element held at one end in said opening and aphonograph needle chuck cemented to such piezoelectric element in linetherewith at its other end;

and stop means on said casing halves for limiting lateral movements oisuch needle chuck and piezoelectric element; the method of assemblingsaid device comprising the steps of assembling one end of saidpiezoelectric element into the opening in said resilient members andsaid resilient members into said casing halves to form a nalsub-assembly, disposing said needle chuck with one end in functionalrelationship to be with the other end of said piezoelectric element andwhile so disposed holding said needle chuck substantially midway betweensaid stops and in stress-free relationship with said piezoelectricelement, and cementing said needle chuck and said piezoelectric elementtogether while said needle chuck is so disposed.

3. In a phonograph translating device including a pair of casing halvesheld together to form a casing; a pair of resilient members inside ofsaid casing halves and having an opening therein; a pickup unitincluding, a piezoelectric element held at one end in said opening Ianda phonograph needle chuck cemented to such piezoelectric element in linetherewith at its other end; and stop means on said casing halves forlimiting lateral movements of such needle chuck and piezoelectricelement; the method of assembling said device comprising the steps ofassembling one end of said piezoelectric element into the opening insaid resilient members and said resilient members into said casinghalves to form a final subassembly, disposing said needle chuck with oneend in functional relationship to be with the other end of saidpiezoelectric element and while so disposed shimming said needle chuckto lie substantially midway between said stops and in stress-freerelationship with said piezoelectric element, cementing said chuck andsaid piezoelectric element together while said needle chuck is sodisposed and held, and removing said shims.

4. In a phonograph translating device including a pair of casing halvesheld together to formV a casing; a pair of resilient members inside ofsaid casing halves and having an opening therein; a pickup unitincluding, a piezoelectric element held at one end in said opening and aphonograph needle chuck cemented to such piezoelectric element in linetherewith at its other end; and stop means on said casing halves forlimiting lateral movements of such needle chuck and piezoelectricelement; the method of assembling said device comprising the steps ofassembling one end of said piezoelectric element into the opening insaid resilient members and said resilient members into said casinghalves to form a final subassembly, disposing said needle chucksubstantially midway between said stops with the appropriate end of saidneedle chuck'in functional relationship to be with said other end ofsaid piezoelectric element and in stress-free relationship therewith,and cementing said needle chuck and said piezoelectric element togetherwhile said needle chuck is so disposed.

5. In a phonograph translating device including a pair of casing halvesheld together to form a casing; a pair of resilient members inside ofsaid casing halves and having an opening therein; a pickup unitincluding a piezoelectric element held at one end in said opening; and aphonograph needle chuck having a pair of prongs each of which lies onone side respectively of the other end of such piezoelectric element,said prongs being cemented to such piezoelectric elemnt with the chuckin line therewith; and stop means on said casing halves for limitinglateral movements of such needle chuck and attached piezoelectricelement; the method of assembling said device comprising the steps ofassembling one end of said piezoelectric element into the opening insaid resilient members and said resilient members into said casinghalves to form a final subassembly, disposing said needle chucksubstantially midway between said stops with each of said prongs lyingon respective sides of said piezoelectric element and in stress-freerelationship therewith, and cementing said prongs and said piezoelectricelement together while said needle chuck is so disposed.

6. In a phonograph translating device including a pair of casing halvesheld together to form a casing; a pair of resilient members inside ofsaid casing halves and having an opening therein; a pickup unitincluding a piezoelectric element held at one end in said opening; and aphonograph needle chuck having a pair of prongs each of which lies onone side respectively of the other of such piezoelectric element, saidprongs being cemented to such piezoelectric element with the chuck inline therewith; and stop means on said casing halves for limitinglateral movements of such needle chuck and attached piezoelectricelement; the method of assembling said device comprising the steps ofassembling one end of said piezoelectric element into the opening insaid resilient members and said resilient members into said casinghalves to form a final subassembly, disposing said needle chuck witheach of said prongs lying on respective sides of said piezoelectricelement and while so disposed holding said needle chuck substantiallymidway between said stops and in stress-free relationship with saidpiezoelectric element, and cementing said needle chuck and saidpiezoelectric element together while said needle chuck is so disposed.

LEE GNTER, JR.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,352,311 Di Toro June 27, 1944 2,363,497 Begun Nov. 28, 19442,518,861 Burtch Aug. 15, 1950

